Paraffin is one of the most widely used waxes for making candles and as water-proofing agent for packaging and food industries. The use of paraffin is dictated by a combination of its desirable properties, including melting profile, hardness, cohesiveness, clarity, and heat stability. According to a study by The Freedonia Group, U.S. demand for waxes is to grow at a rate of 1.8% annually through 2019. However, because paraffin is a petroleum based product, it is not sustainable, nor recyclable or biodegradable. Due to the environmental issues caused by three billion pounds of paraffin-coated corrugated paper products being sent to landfills every year, the demand for a “green” material continues to increase. Many are seeking alternatives, and vegetable oil has been studied as a desirable potential raw material for the production of waxes having properties comparable to those of paraffin.
Paraffin is a mixture of saturated hydrocarbons that contain 80-90% linear chains with an average of 20-30 carbons (Palou et al., “Characterization of the Composition of Paraffin Waxes on Industrial Applications,” Energy Fuels 28(2): 956-63 (2014)). The properties of refined paraffin depend on the proportion of the linear and branched chains in the hydrocarbons. A high concentration of branched chains leads to undesirable oily surface and can negatively affect physical properties such as hardness, friction resistance, melting point, consistency, and clarity (Palou et al., “Characterization of the Composition of Paraffin Waxes on Industrial Applications,” Energy Fuels 28(2): 956-63 (2014)).
Vegetable oil-based waxes are typically obtained by modifying the composition or structures of fatty acids, such as partial or full hydrogenation, and interesterification, to achieve desired physical properties. Other chemical modifications are also used to attach functional groups on the acyl chain to achieve certain desirable properties. Several studies have reported that incorporating hydroxyl groups, branched chains, and short-chain fatty acids could improve the cohesiveness of vegetable oil-based waxes (Feuge et al., “Modification of Vegetable Oils. XII. Plasticity of Some Aceto Derivatives of Monostearin,” J. Am. Oil Chem. Soc. 29:11-14 (1952); U.S. Pat. No. 5,434,278 to Pelloso et al.). However, very few studies systematically studied the structure-functionality relationships.
Despite the efforts made in these modifications to the composition or structures of fatty acids, vegetable oil-based waxes still are not widely used on a commercial scale, because of their limitations in delivering desired physical properties, e.g., they are either too hard and brittle or too soft and greasy, and have poor melting and recrystallization profiles. Fully hydrogenated soybean oil (FHSO) alone is not suitable for making candles or as coatings because of its brittle texture. Though introducing branched groups into the fatty acyl chain by epoxidation, ring opening, and esterification improved its cohesiveness, such materials had a significantly lower hardness and melting point compared to the commercial paraffin (Wang et al., “Chemical Modification of Partially Hydrogenated Vegetable Oil to Improve its Functional Properties for Candles,” J Am Oil Chem. Soc. 84:1149-59 (2007)). Increasing the structure heterogeneity and the amount of hydroxyl groups or incorporating other functional groups, such as using partial acylglycerols, may also improve cohesiveness by interfering orderly packing and improving intermolecular interaction. For example, a study showed that incorporating acetyl and hydroxyl groups in FHSO improved its cohesiveness. However, hardness suffered in an acetylated FHSO. Also, the use of stearyl alcohol for deriving long-chain and linear esters could improve hardness, but it lowered cohesiveness (Yao et al., “Synthesis and Characterization of Acetylated and Stearylyzed Soy Wax,” J. Am. Oil Chem. Soc. 90: 1063-71 (2013)). To date, no good biorenewable material to replace petroleum paraffin has been identified.
Therefore, there remains a strong need to obtain various biodegradable wax materials that can be derived from renewable raw materials, with a high melting point, high cohesiveness, high hardness, high clarity, good water repellency, and low coefficient of surface friction suitable to replace petroleum paraffin. The present invention is directed to fulfilling this need in the art.